Brain cancer is a leading cause of cancer death and it is a deadly disease with a poorly understood etiology. The most consistent risk factor is ionizing radiation, and the genetic and environmental risk factors are unknown. It has been suggested that N-nitroso compounds or foods high in them may be a major contributor to cancer risk. The proposed research focuses on the association between dietary N-nitroso intake and brain cancer. The hypothesis that N-nitroso compounds are associated with human brain cancer is supported by several lines of evidence. First, animal experiments have shown the N-nitroso compounds to be the most broad acting and the most potent group of carcinogens. Second, mechanisms how N-nitroso compounds promote DNA damage and lead to carcinogenesis have been described. Finally, some, but not all epidemiological studies evaluating the role of N-nitroso compounds have shown a positive association or increased risk of stomach and upper gastro-intestinal tract cancers, colorectal cancer, and brain cancer. However, most dietary epidemiological studies have measured intakes of N-nitroso compounds poorly, used surrogate or incomplete measures, and had low statistical power. Therefore, a validated instrument for the dietary assessment for N-nitroso intake using appropriate nutritional, biometric, and epidemiological techniques is needed. The goal of this developmental project is to use quantitative techniques to develop a valid, reliable, and sensitive tool for assessing N-nitroso dietary intake in adults, and then retest the association between N-nitroso intake and brain cancer. Ultimately the methodology will support subsequent investigations in the rapidly developing area of genetic and molecular epidemiology, and help understand genetic and dietary interactions of N-nitroso compounds in the development of brain and other cancers.